Rice

Biotechnology has created Green Revolution rice able to produce high yields when supplied with nitrogen fertiliser and managed intensively.

As a tropical crop, it can be grown during the two distinct seasons (dry and wet) of the year provided that sufficient water is made available.

Abiotic factors include the soil type, whether lowland or upland, amount of rain or irrigation water, temperature, day length, and intensity of sunlight.

Mechanical transplanting takes less time but requires a carefully-prepared field and seedlings raised on mats or in trays to fit the machine.

The usual arrangement is for lowland fields to be surrounded by bunds and flooded to a depth of a few centimetres until around a week before harvest time; this requires a large amount of water.

[11] Across Asia, unmilled rice or "paddy" (Indonesian and Malay padi), was traditionally the product of smallholder agriculture, with manual harvesting.

Oryza sativa rice was first domesticated in China 9,000 years ago,[16] by people of Neolithic cultures in the Upper and Lower Yangtze, associated with Hmong-Mien-speakers and pre-Austronesians, respectively.

[26][27] It was also carried into Taiwan by the Dapenkeng culture by 5500 to 4000 years ago, before spreading southwards via the Austronesian migrations to Island Southeast Asia, Madagascar, and Guam, but did not survive the voyage to the rest of the Pacific.

[31] The now less common Oryza glaberrima (African rice) was independently domesticated in Africa around 3,000 years ago,[31] and introduced to the Americas by the Spanish.

[32] In British North America by the time of the start of the American War of Independence, rice had become the fourth most valuable export commodity behind only tobacco, wheat, and fish.

[38] Rice is a major food staple in Asia, Latin America, and some parts of Africa,[39] feeding over half the world's population.

In a reference serving of 100 grams (3.5 oz), cooked white rice provides 130 calories of food energy, and contains moderate levels of manganese (18% DV), with no other micronutrients in significant content (all less than 10% of the Daily Value).

[68][69] In the Po Valley in Italy, the arborio and carnaroli risotto rice varieties have suffered poor harvests through drought in the 21st century.

Rice yield can be reduced by weed growth, and a wide variety of pests including insects, nematodes, rodents such as rats, snails, and birds.

[78] Sustainable pest management is based on four principles: biodiversity, host plant resistance, landscape ecology, and hierarchies in a landscape—from biological to social.

[82] Farmers in China, Indonesia and the Philippines have traditionally managed weeds and pests by the polycultural practice of raising ducks and sometimes fish in their rice paddies.

These produce valuable additional crops, eat small pest animals, manure the rice, and in the case of ducks also control weeds.

[85] Conversely, other chemicals, such as the insecticide imidacloprid, appear to induce changes in the gene expression of the rice that make the plant more susceptible to certain pests.

[94] Ventria Bioscience has genetically modified rice to express lactoferrin and lysozyme which are proteins usually found in breast milk, and human serum albumin.

[95] Rice containing these added proteins can be used as a component in oral rehydration solutions to treat diarrheal diseases, thereby shortening their duration and reducing recurrence.

[98] Standard rice varieties cannot withstand stagnant flooding for more than about a week, since it disallows the plant access to necessary requirements such as sunlight and gas exchange.

[97] So-called "scuba rice"[99] with the Sub1A transgene is robustly tolerant of submergence for as long as two weeks, offering much improved flood survival for farmers' crops.

[101][102] Under drought conditions, without sufficient water to afford them the ability to obtain the required levels of nutrients from the soil, conventional commercial rice varieties can be severely affected—as happened for example in India early in the 21st century.

[102] In addition, in 2013 the Japanese National Institute for Agrobiological Sciences led a team which successfully inserted the DEEPER ROOTING 1 (DRO1) gene, from the Philippine upland rice variety Kinandang Patong, into the popular commercial rice variety IR64, giving rise to a far deeper root system in the resulting plants.

[103][104] Soil salinity poses a major threat to rice crop productivity, particularly along low-lying coastal areas during the dry season.

[106] These high concentrations of salt can severely affect rice plants' physiology, especially during early stages of growth, and as such farmers are often forced to abandon these areas.

[108] Developed by the International Rice Research Institute, the hybrid variety utilises specialised leaf glands that remove salt into the atmosphere.

It was produced from one successful embryo out of 34,000 crosses between the two species; this was then backcrossed to IR56 with the aim of preserving the genes responsible for salt tolerance that were inherited from O.

Putting the barley gene SUSIBA2 into rice creates a shift in biomass production from root to shoot, decreasing the methanogen population, and resulting in a reduction of methane emissions of up to 97%.

[115] The start of the rice planting season is marked in Asian countries including Nepal and Cambodia with a Royal Ploughing Ceremony.